Climbers use various types of active and passive devices as protection against falls. Active devices generally include some kind of mechanical parts that assist in anchoring the protection on the rock wall. A cam is an example of an active device. Passive devices, on the other hand, do not include mechanical parts for attachment to the rock, and instead rely upon friction and gravitational forces to achieve anchoring. One type of passive protection is a climbing nut, which may also be referred to as a chock.
Climbing nuts are made in many different shapes, but many are generally formed as trapezoidal wedges. During a climb, nuts of appropriate size are wedged into cracks in the rock and a climbing rope is connected indirectly to the nut through various slings and like devices. To ensure proper placement of the nut (i.e., the "protection") it is important that the protection is not moved once it is set in the crack, such as being rocked back and forth in the crack as the rope moves through the attached carabiner. Therefore, each nut includes a loop or sling of cable attached to it. A carabiner is typically attached to the cable and a loop of webbing is attached to the carabiner. Another carabiner is then connected to the opposite end of the webbing and the rope is passed through the second carabiner. This system allows the rope to move freely through the carabiners without unduly moving the nut and risking its coming loose.
The wedge shape allows the nut to be pulled upwardly to release it from its engagement with the rock. As a climber progresses up a climb the nuts may be pulled upwardly and out of the crack when they are no longer needed. The nut may then be reused on the next pitch. On the other hand, if a climber falls the wedge shape of the nut provides a secure anchor, as the climbing rope becomes taut during the fall, thereby arresting the climber's fall.
Proper placement of nuts is obviously very important since improper placement can lead to failure of the protection when it is most needed. One important aspect of the placement is the attainment of triangulation between the nut and the rock. In other words, for proper holding strength it is important that there are at least three points of contact between the nut and the rock. When the nut is properly seated in a crack with proper triangulation the nut provides adequate anchoring strength. However, cracks in rocks are rarely regular in geometric shape. They are, instead, typically curved and irregularly shaped. Moreover, many cracks flare either inwardly or outwardly. With such irregular rock formations it can be difficult in some cases to visually verify that nut placement has achieved correct triangulation.
With standard nuts that are trapezoidal in shape with opposed straight tapered faces the nuts tended to have only two points of contact with the rock. Two points of contact is insufficient for a variety of reasons, including insufficient holding strength, and also the tendency of the nut to pivot back and forth in the rock about the two contact points as the rope moves through the attached carabiners. This pivoting can lead to loosening of the protection and in extreme cases can lead to the nut coming out of the crack. However, with nuts having this geometry visual verification of placement in a crack is relatively easily accomplished.
Various shapes of nuts have been designed over the years to improve placement options and to improve triangulation. As noted, one standard shape is a straight-sided wedge with a constant taper angle. Nuts with this shape are ubiquitous and may be beneficially used in many situations. But given the irregularities in the shapes of cracks, such nuts have limited placement options. Further, while visual verification is easy, unless a crack is relatively straight-sided and the contours of the crack match the geometry of the nut, it can be very difficult to attain proper triangulation. As would be expected, it is a relatively rare occasion when the geometry of a crack conforms to the geometry of a nut. This can lead to the nut pivoting or rocking back and forth in the crack.
Various nut designs have been implemented to increase holding ability and the ability to verify correct placement. One such design shown in U.S. Pat. No.4,083,521 comprises a "trefoil" nut having three equiangular arms radially extending from a center point. The body of the nut is generally trapezoidal as viewed in a side elevation. The patent notes that the device allows for easy placement and retrieval. However, while this nut does improve the ability to achieve triangulation, it presents limited placement options given the equiangular and equal length radial arms. In addition, visual verification of proper triangulation is difficult.
Another improved nut design is disclosed in U.S. Pat. No. 4,422,607. The nut described in that patent is generally wedge shaped, but two opposite faces of the nut are respectively concave and convex, with the cylindrical axis of the concave and convex curvature extending transverse to the vertical axis through the nut. The nut described in this patent is an improvement over wedge shaped nuts having straight tapering sides since with it triangulation is more easily accomplished. However, with this nut it can be difficult to visually ensure that the nut is properly placed. More particularly, in some placement situations it can be difficult to visually determine if the nut of the '607 patent will be prone to rock out of the placement if a sudden load is placed on the nut, as in a fall. This is because the axis of the curved faces extends across the nut, transverse to the axis along which a load is placed during a fall. Thus, with this geometry it is difficult to verify proper placement in many types of cracks. As noted, many cracks exhibit either inward or outward flaring. Given the geometry of the nut of the '607 patent, placement of the nut in flared cracks is difficult and verification of proper placement is likewise difficult.
Other nuts having a modified wedge shaped have also been developed. For example, in one prior art trapezoidal shaped wedge nut, both opposed "wide" faces of the nut are concave with the cylindrical axis of the concave sections extending generally parallel to the long axis through the nut, and thus parallel to the direction that a load is exerted in a fall. The concave sections define longitudinal rails along the outer sides of the faces. The side faces are planar. In one modified embodiment of this kind of a nut the wide faces have a radius of curvature rather than having a straight sided taper and the top and bottom surfaces are not co-planar. With these nuts, triangulation, while difficult in some crack contours, is generally improved. However, visual inspection tends to be difficult.
There is a need therefore for a climbing nut that improves on prior nuts, provides improved protection and holding strength, provides for more placement options in cracks having varying geometry, and which allows for quick and accurate visual verification of placement.
Prior art nuts such as those described above are typically manufactured by casting, or by cutting extruded stock into desired lengths. For example, the nut described in the '521 patent described above is said to be manufactured from extruded metal or plastic stock. Nuts such as those shown in the '607 patent may also be cut from extruded stock. An alternative method of manufacturing nuts is by well-known forging or casting techniques. With nuts that have variable geometry and multifaceted faces, it is not possible to make suitable extrusion stock material. Moreover, even if stock material could be made it is not always possible or economical to cut the stock into lengths with the cut faces having the proper geometry. In such cases casting is an acceptable alternative method of making the nut.
Both the extrusion and casting methods work well, but both have limitations. For instance, with the extrusion method there are severe limits on the angular geometric face shapes that can be produced. And if the lateral cut sides of the nut are to be any shape other than planar, extrusion cutting is essentially impossible. Cast nuts may be manufactured in virtually any shape. However, casting is a time consuming and sometimes difficult process that requires special equipment. Molds must be made for each specific geometric shape, and quality control over the alloys used must be closely watched.
There is a need therefore for alternative methods of manufacturing nuts having multifaceted faces.